Catalytic hydration of olefins



Patented Nov. 10, 1953 CATALYTIC HYDRATION OF OLEFINS Sigmund J.Lukasiewicz, William I. Benton, and Charles J. Plank, Woodbury, N. Jassignors to Socony-Vacuum Oil Company, Incorporated, a corporation ofNew York g No Drawing. Application July 5, 1950,

Serial No. 172,188

1 Claim. 1

This invention relates to a process for the catalytic hydration ofolefins having three to five carbon atoms to produce alcohols and isspecifically concerned with provision of a novel catalyst capable ofproducing high yields of the desired alcohols.

The novel catalyst with which the invention is concerned is a compositeof silica and alumina prepared by precipitating silicon dioxide onpcrous alumina. Preferably the catalyst contains about to about 25%S102. Minor amounts of various activating oxides may also be present, asfor example, around one weight per cent or a little more of the oxidesof silver, mercury, tin, tungsten and the like. However, the catalystmust be substantially free of alkali metal oxides which have a stronginhibiting effect on the catalyst. The alkali metal content should beless than about 0.5% and is preferably reduced to as low a value as canbe achieved economically.

Porous catalysts have been proposed for hydration. Specifically, the useof alumina, which may be activated as by impregnation with acid saltssuch as aluminum sulfate, has been described. The theory on which thesecatal sts are proposed appears to be analogous to the older sulfuricacid process since the modified alumina catalysts are characterized forthe most part by anions of strong mineral acids incorporated either bytreatment with acid or by impregnation with an acid reacting salt.

It has now been discovered that silica-alumina composites as describedabove are superior catalysts for the catalytic hydration of olefinshaving three to five carbon atoms. These novel catalysts arecharacterized by substantial absence of anions of strong acids andcations of strong bases. The present catalysts normally contain suchions during the process of manufacture. However, the manufacture isconducted in such manner that these components are removed from thecatalyst before it is finished. Thus, the base alumina may be formed byprecipitation from a sol prepared by mixing sodium aluminate andsulfuric acid solutions. During manufacture, sodium is removed by waterwashing until free of sodium and acid anions.

These catalysts are effective for conversion to alcohols of propylene,butenes and amylenes.- No yield of product is obtained when ethylene istreated under conditions similar to those found effective for olefins ofthree to five carbon atoms. As the number of carbon atoms is increasedabove three, the yields are reduced to such an extent that the processis not found practicable for olefins Isix r mo ca o a oms- In conductingthe hydration reaction, olefin vapor is contacted with the catalystunder suitable conditions of temperature and pressure in the presence ofa molar excess of water with respect to olefin. At least part of thewater is also in vapor phase and this reactant may be wholly vaporous orpartly liquid. The concepts of mixed phase operation and of waterpretreatment for improving the catalytic reaction are described andclaimed in copending application Serial No.

127,168, filed November 14, 1949. Since the novel methods of conductingthe reaction described in the said copending application result inincreased efliciency, many of the examples set out hereinafter utilizethose concepts. The present invention, however, is not restricted tosuch operation, since the novel catalyst exhibits its advantages inhydration of C3 to C5 olefins generally.

The present catalysts are, in general, active for promoting a largenumber of hydrocarbon reactions and mention is made of polymerization,cracking and hydrogen transfer as important side reactions in connectionwith catalytic hydration. These side reactions result in formation ofpolymers, saturated hydrocarbons and dense solid deposits of high carboncontent referred to herein as coke. The side reactions also result information of oxygenated compounds such as ketones and, in someinstances, esters and other byproducts.

The commercial desirability of catalytic hydra tion of olefins toproduce alcohols is related to ability to obtain conversions of olefinsto reasonable amounts of alcohols without degradation of the olefin notconsumed in the production of alcohols to by-products of little or novalue compared to the charge stock and desired product.

The method for conducting the catalytic hydration described in saidcopending application greatly increases the selectivity of the reaction;that is, increases the percentage yield of alcohol based on olefinconsumed. It has been found possible to conduct the operation in suchmanner that the selectivity approaches in the case of propylene. Aselectivity of 99% is readily obtained with high single-pass yields ofalcohol based on total olefin charge to the reaction.

The conditioning of the catalyst by preliminary water treatment resultsin a drastic reduction of surface area of the porous solid, aresult'which is generally regarded as undesirable in connection withporous catalysts. In typical instances the fresh catalyst is reduced toabout one tenth its original surface area on the initial conditioningtreatment before beginning the first run.

This conditioning treatment results in a cat- 2,ese,924

alyst which gives increased yields of alcohols and very low yields ofsaturated hydrocarbons, coke, ketones, and the like. Not only does thisindicate a greater efficiency in that the olefin consumed is morelargely converted to the 'desiredproduct, but it furthergivesanimportant commercial advantage in that the conversion runs may be mademuch longer between regenerations of the catalyst to remove cokedeposits. Thus an unconditioned catalyst can be run for "3 or 4 hoursbefore coke contamination becomes so serious that the catalyst must beregenerated by burning. When catalysts are properly conditioned,conversion runs of several weeks or months are possible withoutregeneration of the catalyst.

The pretreatment of the catalyst'is conducted at a temperature withinthe range effective for catalytic hydration of olefins. Preferably thepressure of conditioning treatment is also within the catalytichydration range, thereby obviating necessity for a separate. pressuringstep before placing the catalyst on stream forcatalytic hydration. Thewater used forconditioning treatment of the catalyst may vbein eitherliquid .or gaseous phase; in general, phase of the condi tioning wateris determined by the phase desired in the subsequent hydration treatmentas willappear from the following-discussion of a preferred embodiment ofthis invention. Where water vapor is employed, pressures upwards of 500pounds per square inch are preferred.

In addition to the advantages arising from conditioning the catalyst bytreatment with water, further improvements in operation follow uponmaintaining water in the liquid phase within the bed of catalyst duringthecatalytic hydration treatment. This expedient, which is referred toherein as the flooded reactor technique seems to derive its advantagefrom the fact that the presence .of liquid water in the reactor permitsoperation of the process at very high mol ratios of water to olefinwithout necessity for handling comparable quantities of water in thesubsequent recovery equipment. When the process is operated wholly inthe vapor phase, it is found that the mol ratio of water to olefin inthe charge is an important factor with respect to yield of the desiredproduct. A true vapor phase reaction operates best at a mol ratio of :1and thus requires that the recovery equipment be adapted to handletremendous quantities of watar as compared with the quantities ofalcohol and unconverted olefin leaving the reaction zone.

By way of contrast, the flooded reactor technique makes it possible tocharge a mixture halling a water to olefin mol ratio of about 2 .andpassing an equivalent quantity of water with the reaction eiliuent tothe recovery equipment. The mol ratio in the reaction zone is, however,tremendously higher and may be on the order of 50 or 100:1.

Catalytic hydration of .olefins according to this invention may beconducted over a wide range of conditions. In general, elevatedtemperatures are necessary, in excess of 250 F. for flooded reactoroperation and above about 300 F. for vapor phase reactions. It isdesirable to operate below temperatures at which extensive crackingoccurs and for this reason the maximum desirable temperature is about700" F. Best operations are obtained at 350-500 F. for flooded reactor,preferably 400-450" F., and 550-650 F., preferably 600 F. for vaporphase reactions. Elevated pressures are necessary for good operamust beadjusted relative to the temperature to maintain the phase relationshipsdesired. Pressures of 375-3000 p. s. i. g. are suitable but betterconditions are found between 750 and 2000 p. s. i g. Itis preferredtoperate at about 1000 pounds under flooded :reactor conditions and atabout 1500 pounds for vapor phase reactions.

.Pressures above 3000 p. s. i. g. increase conversion but also increaseprocessing difliculties.

The two types of operation, namely vapor phase and flooded reactor,differ greatly with respect to desirable :mol ratios of water tohydrorcarbonandspace velocity. As used herein space velocity referstovolumes of liquid'feed per hour per volume of catalyst space. Desirablemol ratios are controlled by two opposing considerations. The higher themol ratio, the greater the selectivity of the process but increased molratios also increase the costs of handling large quantities of excesswater in charge preparation and productrecovery. Vapor phase reactionsoperate satisfactorily at .mol ratios between 5 and 20:1, preferablybetween 7 and 15:1 with .optimumresults inthe neighborhoodof 10:1. Underflooded reactor conditions external mol ratios between .0.5 and 5:1 aresuitable with preference .for ratios between -1 and .311. The optimum isabout 2:1.

The vapor phase reactions may be conducted at space velocitiespreferably between 1 and 5 with an optimumat about 3. Space velocitiesfor flooded reactor operation may vary between 0.2 and 5.0, preferably0.5 to 2.0, the minimum of the preferred range being about optimum.

In the following examples, it is demonstrated that, in general,coprecipitated and like homogeneous silica-alumina catalysts forhydration should contain from .1 to 35 per cent of alumina. This is theprinciple underlying copending application Serial No. 153,306, filedMarch 31, 1950, and now abandoned. However, when the catalyst is formedby precipitating silica on alumina, these limits no longer apply. It isquite apparent that the active surface so formed will be predominantlysilica. The present results are therefore not inconsistent with thegeneral principle.

Example I A silica-alumina bead catalyst (see Marisic Patent 2,384,946)containing silica and 10% alumina by weight and substantially free ofsodium oxide was treated with water at 590 F. and a pressure of 1500 p.s. i. g. A total volume of 500 ml. of catalyst was thus contacted with975 ml. of water at 2. space velocity of about 2 in the absence ofolefin. Thereafter a mixture containing 924 grams (22 mols) of propyleneand 3991 grams (222 mols) of water was brought to 590 F. and passedthrough the catalyst at a pressure of 1500 p. s. i. g. and a spacevelocity of 3. After 4 hours of operation, 111 grams of pure isopropylalcohol was produced. This represents a yield of 12 weight per cent ofthe alcohol based on propylene charged. Further data on the run areshown in the table below.

Example II The catalyst of this example was a silica-alumina compositecontaining 87.5% S102 and 12.5% mm. The catalyst was prepared byco-precipitation, washed, base exchanged for removal of sodium and waterwashed until the eilluent was free of salts removed from the gel.Thereafter the gel was kneaded to form a heavy slurry, cast tion and itwill be apparent that the pressure ((5 in perforated steel plates, anddried. A total volume of 500 f lyst was pretreated with '500 ml. ofwater at 587 F., 1500- p. s;i.'g.-'and a space velocity of 1. The chargewas made'up by mixing 247 grams (5.9 mols) of propylene and 1000 gramsof water (55.5 mols) and charged to run.

Example III The two preceding examples illustrate vapor phase reactionand the present example is concerned with anoperation under floodedreactor conditions. A total of 500 ml. of catalyst as described inExampl I was treated with 500 grams of water maintained in liquid phaseat 412 F.,

750 p. s. i. g. and a space velocity of 1.0. The charge mixture was madeup of 346 gram (8.3 mols) of propylene and 300 grams (16.7 mols) ofwater which was pumped over a period of 4 hours through the reactorunder the same temperature and pressure conditions as those prevailingfor the pretreatment and spac velocity of about 0.5. As a result of thepretreatment, the reactor was filled with liquid water prior to theintroduction of the charge which bubbled up through the'water in thereaction space. The product contained 38 grams of pure isopropyl alcoholrepresenting a yield of 11% by weight based on propylene charged.

Example IV Straight silica gel was used as the catalyst under floodedreactor conditions with a yield of 1.5 isopropanol. A total volume of500 ml. of catalyst was treated with 500 grams of water at 430 F. and750 p. s. i. g. Thereafter, a mixture of 512 grams of propylene (12.2mols) and 455 grams of water (25.3 mols) was passed through the catalystat a space velocity of 1.0, a temperature of 430 F. and a pressur of 750p. s. i. g. over a period of 3 hours.

Example V Activated alumina was conditioned by treatment with steamunder conditions similar to those of the reaction. Subsequent reactionof a :1 mixture of water and propylene at a space velocity of 3 for 3hours at 595 F. and 1500 p. s. i. g. on the conditioned catalyst gave ayield of 4.9% isopropanol. Further details in the table.

Example VI The results using alumina gel were relatively poor as shownin the table.

Example VII A co-precipitate of silica and alumina containing 75% silicaand 25% alumina conditioned by steam gave a yield of 10.5% isopropanolat 99% selectivity.

Example VIII A co-precipitated gel containing 57% S102 and 43% A1203 wastreated with 500 cc. of water at 595 F. and 1500 p. s. i. over a periodof one hour. The hydrocarbon was then added without stopping the wateraddition. 2411 grams (134 mols) of water and 561 grams (13.4 mols) ofpropylene were pumped over a period of two and one half hours at a spacevelocity of 3.0, 595 F., and 1500 p. s. i. No alcohol was found in theefliuent.

the catalyst under the same conditions as those stated for the Waterpretreatment, except that the space velocity was increased to 3. DuringA catalyst prepared by impregnating A1203 with S102 to prepare afinished catalyst of 25 weight per cent S102 was pretreated with liquidwater under reaction conditions. Whil keeping the catalyst wet withliquid water, a reactionmixture of 2 mols of water per mol of propylenewas pumped through the catalyst at 1500 p. s. 1., 425

F., and a space velocity of 1 for one hour; -The emuent showed a yieldof 10.4 weight percent isopropanol and no polymer. This example dem-.onstrates that the catalytic effect is found at the surface of thecatalyst, Upon impregnation of alumina with silica, a surface is formedin which silica predominates, although a complete analysis would showalumina as the predominant com.- ponent. Apparently the aluminamolecules be:- low the surface are inefiective, since it has beendemonstrated that a homogeneous catalyst of th present composition ispractically useless.

Example XI The catalyst employed was prepared by treating activatedalumina with water glass (0.204 gram SiOz/cc.) in a quantity to give afinished product containing 10% S102 for hour. The catalyst was treatedwith 4 N hydrochloric acid for one hour, washed free of chlorides, ovendried and muflied. The catalyst was treated with water under reactionconditions. The hydration reaction was conducted at 1500 pounds and 430F. with a space velocity of 1.0 during a period of one hour. At a molarratio of two parts of water per part of propylene, the isopropanol yieldwas tivity Example XIII In this example the activated alumina wastreated with suflicient ethyl silicate to give 2% SiOz in the finishedcatalyst. The impregnating solution in alcohol contained 0.270 gram8102/ cc. The impregnated alumina was oven dried and muflied at 1000 F.The catalyst was then treated with liquid water at reaction conditionsand utilized in the hydration of propylene. During a 1.5 hour run amixture of 4.5 mols of water per mol of propylene was passed through thecatalyst at a space velocity of 1.0, pressure of 1500 pounds andtemperature of 408 F. The yield of isopropanol was 1.07% at 99%selectivity.

Example XIV This run diil'ered from Example XIII in that the alumina wasimpregnated with ethyl silicate to give a final catalyst containing 10%SiO2, the water to propylene mol ratio was 4.9 and the reactiontemperature was 435 F. The yield of isopropanol was 11.0% and theselectivity 99%.

Map

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SIGMUfiD J. LUK'ASIEWICZ.

I. fiENTON.

(Rusii, v01. 14, page 1:?63 (1946).)

